Annually, millions of Americans suffer from significant spine related pain and discomfort. Where the cervical, thoracic, and lumbar vertebrae and discs can be the source of this pain and discomfort. In one estimate, pain perceived in the neck or upper limbs that is caused by irritation in the nerves that exit the cervical spine through the foramen affects a population of approximately 1 person per 1000 per year. As a result, every year physicians in the United States perform an estimated 750,000 transforaminal cervical injections to treat these patients.
While the nerve irritation and resultant inflammation causing this spinal pain has a variety of etiologies that result in contact between the nerve and the adjacent structures in the spine, transforaminal injections of corticosteroids can relieve this irritation and reduce the accompanying pain.
Injections of corticosteroids and or local anesthetics into isolated areas of the epidural space are important treatment and diagnostic modalities for patients suffering from spinal pain syndromes. Isolation of the injection to a specific spinal level is accomplished by using a transforaminal approach. This is distinguishable from the traditional trans-laminar approach of spinal epidural injections commonly used for anesthesia.
Presently, physiatrists, anesthesiologists, radiologists, neurologists, and orthopedic surgeons perform such transforaminal injections under fluoroscopic guidance using a C-Arm fluoroscope, a standard spinal needle, and three 3 cc syringes. One current technique in providing these injections includes conscious sedation of the patient through the use of local anesthetic and anxiolytics. The operator performs the procedure using multi-plane fluoroscopy to guide the needle into position and to verify correct location of the delivery device prior to injection of the substance.
As shown in FIG. 1A, existing delivery devices include a 20-25 gauge hypodermic needle 1 that is inserted through the skin, muscle and soft tissues 10. Using fluoroscopy, the operator positions the distal end of the needle immediately adjacent to a portion of a vertebral body 12 at the level of the desired injection. Typically when delivering the injection in a cervical region of the spine, this includes positioning the tip of the needle immediately adjacent to a posterior inferior aspect of a superior articular process 14 of a facet joint of the vertebral body 12 at an index foraminal level chosen for the injection. Care must be taken to avoid puncturing the vertebral arteries or veins 16 extending through foramens in the vertebral body 12.
To test the initial placement of the needle it is standard for the operator to initially inject a contrast media, such as a radio opaque dye. This step is useful to determine whether the needle is undesirably located in a blood vessel 16 or in the dural membrane 18. To verify whether the needle is desirably placed, the operator observes under fluoroscope for negative indication of veneous, arterial, or cerebrospinal uptake of the dye. Upon confirming the correct location, the needle is left in position while the syringe containing the radio opaque dye is carefully removed from the needle and replaced by a syringe containing a local anesthetic such as lidocaine. As explained below, the operator must take great care not to avoid any inadvertent movement or advancement of the needle especially during exchange of the syringes.
The operator then injects a small bolus of lidocaine (or a local anesthetic of choice) and waits a sufficient period (e.g., sixty seconds) to allow for the anesthetic to disperse. During this time the operator observes the patient for adverse reactions resulting from accidental vascular uptake or injection into the dural sleeve or thecal sac. Although placement of the needle was observed using the radiopaque dye, there is still a risk of accidental vascular injections because the needle may have moved during the syringe exchange process or simply because vascular perforation was not detected during the radiopaque dye injection.
Once the operator confirms negative adverse reactions, the operator again carefully exchanges syringes to connect a syringe containing a corticosteroid. Finally, the corticosteroid is injected in an effort to reduce inflammation thereby affording the patient pain relief. After the three injections i.e. radio-opaque dye, local anesthetic, corticosteroid are complete, the needle is removed from the patient.
Although the current procedure provides benefits to patients having spinal related pain, significant risk remains with the current procedure. One inherent risk includes breaching a blood vessel and the inadvertent injection of dye, anesthetic, and/or corticosteroids into an artery or vein. Currently, it is believed that breaching a blood vessel occurs in a considerable number of injections performed (a recent clinical study had venous uptake in over 19% of injections performed). Additional risks include contact between the injection needle and the nerve root, which may cause pain along with damage to the dura. Finally, there are risks associated to the operator via exposure to the X-Ray radiation of the fluoroscope, particularly in view of the cumulative exposure as the operator must position the needle as well as exchange syringes a number of times.
The actual breaching of the blood vessel may occur during the initial insertion of the needle into the site, subsequent manipulation of the needle during syringe exchanges, or even movement of the needle as a result of the force applied by the operator during actuation of the syringe. In some cases, injection into a blood vessel may occur even if the needle has not penetrated the vessel wall as the force of the injectant flowing out of the distal tip of the needle can be sufficient cause the injectant to breach the blood vessel wall and enter into the vessel.
Complications from accidental injection of the anesthetic into the vessel can include transient paralysis of the spinal cord. Complications resulting from accidental injections of corticosteroids into blood vessels can include permanent paralysis, permanent blindness (if injected into a vertebral artery), seizures, permanent cognitive dysfunction, physical impairment, and/or death.
Another complication associated with transforaminal injections is inadvertent contact between the needle and nerve root which may cause pain or tingling emanating through the upper extremities. If the needle perforates the dural sleeve, spinal fluid may leak resulting in a transient headache lasting from several hours to several days. If local anesthetic is injected into the thecal sac, temporary paralysis may occur that could result in a cessation of breathing, necessitating emergency intubation of the patient.
In view of the above risks, to ensure patient safety the operator must reposition the needle if he or she suspects that patient harm could occur. In addition, if arterial uptake is suspected, a common recommendation is that the procedure should be abandoned to allow the arterial perforation to heal and to obviate the risk of injury to the spinal cord resulting from inadvertent injection of corticosteroid into the radicular artery or vertebral artery.
Each time the needle is repositioned, a new X-Ray image must be captured to verify the needle position and additional real time fluoroscopy images must be captured with an additional injection of contrast media. The additional fluoroscopy and associated radiation exposure presents an increased risk to the operator performing the procedure. To minimize exposure the operator must step toward and away from the radiation field to alternately maneuver or manipulate the hypodermic syringe and allow fluoroscopic images to be taken. This exertion combined with the repeated connecting and disconnecting of syringes contributes to operator fatigue, which is not a trivial consideration for operators performing multiple procedures in a particular day.
The design of the current devices presents an additional problem that contributes to undesired device placement. Current devices include rigid and straight hypodermic needles. Such a configuration limits the operator to only work within the “line of sight” from the surface of the skin along an axis of the needle. In many cases, it is desirable to perform the injection in a position that is not directly accessible by a straight, rigid needle, e.g., it is frequently desirable to inject medicine in a position “behind” portions of the vertebra, nerves, or blood vessels, (i.e. around the corner from the line of sight position).
Devices and methods are provided herein for a transforaminal epidural injection needle system that minimizes the above risks to improve patient safety. In addition, the benefits of such devices reduce operator fatigue and decrease the operator's potential radiation exposure.
The methods and devices may be used for transforaminal selective epidural injections to the cervical, thoracic, or lumbar spine. Fluoroscopically guided, contrast-enhanced transforaminal epidural injection procedures help to specifically evaluate and treat the precise spinal nerve involved as a source of spinal and referred extremity pain. Although therapeutic and diagnostic transforaminal epidural injections have been performed for decades, the equipment used for these injections has been relatively unchanged during that time.